// babel.config.js
module.exports = {
  presets: [
    [
      '@babel/preset-env',
      {
        targets: {
          chrome: '60',
          firefox: '60',
          ie: '11',
        },
        useBuiltIns: 'usage', // 按需添加 polyfill
        corejs: 3, // 必须是 3
        shippedProposals: true, // 启用已交付的提案，包括 .at()
      },
    ],
  ],
};
